How to override parent theme css?

site: http://www.jakespharler.com
theme: twenty-twelve (child theme)

Problem: I was trying to override the style that defines the link color by adding the same code used to define it in the parent theme, just using “none” as the value:

.widget-area .widget a {
color: none !important;
}

However, this did not work. When inspecting with Firebug, I see the code I put in my child theme’s css file, but I also see the default code directly below it, exactly the same, but with a grey color. Question: Isn’t the child theme css suppose to override parent theme css?